A first example of an imaging arrangement for use in this type of display is a barrier, for example with slits that are sized and positioned in relation to the underlying pixels of the display. The viewer is able to perceive a 3D image if his/her head is at a fixed position. The barrier is positioned in front of the display panel and is designed so that light from the odd and even pixel columns is directed towards the left and right eye of the viewer.
A drawback of this type of two-view display design is that the viewer has to be at a fixed position, and can only move approximately 3 centimeters to the left or right. In a more preferred embodiment there are not two sub-pixel columns beneath each slit, but several. In this way, the viewer is allowed to move to the left and right and to perceive a stereo image in his eyes all the time.
The barrier arrangement is simple to produce but is not light efficient. A preferred alternative is therefore to use a lens arrangement as the imaging arrangement. For example, an array of elongate lenticular elements can be provided extending parallel to one another and overlying the display pixel array, and the display pixels are observed through these lenticular elements.
The lenticular elements are provided as a sheet of elements, each of which comprises an elongate semi-cylindrical lens element. The lenticular elements (“lenticules”) extend in the column direction of the display panel, with each lenticular element overlying a respective group of two or more adjacent columns of display pixels.
In an arrangement in which, for example, each lenticule is associated with two columns of display pixels, the display pixels in each column provide a vertical slice of a respective two dimensional sub-image. The lenticular sheet directs these two slices and corresponding slices from the display pixel columns associated with the other lenticules, to the left and right eyes of a user positioned in front of the sheet, so that the user observes a single stereoscopic image. The sheet of lenticular elements thus provides a light output directing function.
In other arrangements, each lenticule is associated with a group of four or more adjacent display pixels in the row direction. Corresponding columns of display pixels in each group are arranged appropriately to provide a vertical slice from a respective two dimensional sub-image. As a user's head is moved from left to right, a series of successive, different, stereoscopic views are perceived creating, for example, a look-around impression.
A lenticular arrangement can be used to create an autostereoscopic display device for any underlying native 2D display panel. However, different display technologies give rise to different technical issues.
This invention is concerned in particular with the combination of shutter based displays with lenticular lens arrangement. The invention is thus directed to a subset of the reflective, transmissive and transflective displays. This type of display has a pixel for which, in one extreme state, the light-modulating part is confined to a small area, and while in the other extreme state, substantial parts of the pixel have this light-modulating property.
Examples of display technology, of which at least some variants are within the scope of this invention, are electrowetting displays, electrophoretic displays, electrofluidic displays and MEMS-type displays.
A problem with the use of this type of display is that the pixel shape and area changes for different grey levels or when making a transition between modulation levels. This can give rise to visual artefacts, particularly when used in conjunction with a lenticular array.